Research On Health Risk Assessment Of Urban Wetlands Based On Dynamic Changes Of Ecological Pattern

Since the construction of ecological civilization was put forward,environmental issues have attracted more and more attention and become a hot issue.As an important part of the urban ecosystem,the wetland ecosystem has changed to a certain extent with the development of urbanization.The health evaluation of the wetland ecosystem is a necessary way to protect and restore the wetland.Based on the Arc GIS platform,this paper divides the land use types into seven categories based on the Landsat remote sensing images,and analyzes each category to study the laws of temporal changes,spatial changes,and changes in the degree of land use.On this basis,the PSR "pressure-stateresponse" model was established,and the Harbin wetland ecosystem health evaluation system was constructed to explore the ecosystem health of Harbin’s urban wetlands.The main contents of this research are as follows:（1）The land use type classification was carried out on the remote sensing images of Harbin in 2000,2005,2010,2015 and 2019.After the accuracy evaluation,the accuracy coefficient was good,indicating that the classification results were reliable.dynamic change analysis.According to the classification results of the fifth phase of land use types in Harbin,it can be concluded that cultivated land occupies the largest area among the land use types in Harbin,with an average area of 45.30%,and forest land occupies the second largest area,with an average area of 43.46%.Wetland occupies a relatively small area,with an average area ratio of 1.87%.According to the analysis of the land use transition matrix and the annual rate of change of single land use,it is concluded that from 2000 to 2019,the area of cultivated land in Harbin has increased every year,the area of construction land has always been increasing,and the area of wetlands has increased,then decreased,and then increased.Irregular increase or decrease.Among them,the wetland area increased the most from 2005 to 2010.The comprehensive index of land use in Harbin has increased year by year,with an increase of 4.72 from 2000 to 2019,indicating that the degree of land use in Harbin still has a certain development potential.Through the calculation of the center of gravity migration model,it is concluded that from 2000 to 2019,the center of gravity of the urban construction land in Harbin has been accelerating to the northwest of the city.（2）Based on the PSR "pressure-state-response" model,the target layer,the criterion layer and the index layer were established,and 11 evaluation indicators were selected according to the relevant conditions of the Harbin wetlands to construct the Harbin wetland ecosystem health evaluation system.Using AHP（Analytic Hierarchy Process）to determine the weight of evaluation indicators,and calculate the wetland ecological health evaluation grade.The pressure layer has a weight of 0.2493,the state layer has a weight of 0.5936,and the response layer has a weight of 0.1575.According to the calculation,the health level of the wetlands in Harbin was 0.35 in 2000,indicating poor health;0.55 in 2005,indicating average health;0.77 in 2010,indicating good health;0.60 in 2015,indicating good health The health status is in the average state;in 2019,it was 0.56,and the health status was in the average state.Overall,the health status of the wetlands in Harbin has turned from poor to better and stabilized.